Why is she being a "bad mommy"?

[wilomn]

Thanks Wes....that makes the most sense. Even if half of the clutch were good, how would she know the bad eggs from the good? If she knows a lot are slugs, then she probably just is giving up on the whole clutch.I guess she's really not being stupid, just "uncaring" or "unmotherly".

Or incredibly efficient.

Why waste energy on eggs that won't hatch?

Systems that have worked for millions of years generally have some good reasons for working for millions of years.